The epothilones e.g. 1(A) and 2(B), FIG. 1B, are a class of molecules having potent cytotoxicity against tumor cells, including Taxol™ (paclitaxel) resistant cell lines. Within this class, it has been observed that cyclopropane- and pyridine-containing analogs of epothilones B and compound 106 exhibit outstanding biological profiles as potential antitumor agents. Herein are disclosed designed analogs of epothilone B characterized by such structural motifs, but having enhanced cytotoxicity against tumor cells and/or enhanced biological profiles as potential antitumor agents.